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V-1-32
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V.1.6.3 Control and operation of iso7816 Mode
transmit control
(1) Clock output
First, start clock output in the following procedure:
1. Set CLKOL1 (D3/0x300B1A) to 1 (forced low output is released).
2. Set CLKOEN1 (D4/0x300B1A) to 1 (clock output begins).
CLKoL1: Serial I/F Ch.1 Clock Output Forced Low Bit in the Serial I/F Ch.1 ISO7816 Mode Control Register
(D3/0x300B1A)
CLKoen1: Serial I/F Ch.1 Clock Output Enable Bit in the Serial I/F Ch.1 ISO7816 Mode Control Register
(D4/0x300B1A)
The clock for asynchronous transfer is output in synchronization with the sampling clock.
SIO_CLK
(Baud-rate timer output)
(Internal clock)
Sampling clock
CLKOL1
CLKOEN1
Clock output enable
#SCLK1 output
Figure V.1.6.3.1 Clock Output Control (example in asynchronous mode)
(2) enabling transmit operation
Use the transmit-enable bit TXEN1 (D7/0x300B13) for transmit control.
When transmit is enabled by writing 1 to this bit, the clock input to the shift register is enabled (ready for in-
put), thus allowing data to be transmitted.
Transmit is disabled and the transmit data buffer (FIFO) is cleared by writing 0 to TXEN1 (D7/0x300B13).
tXen1: Serial I/F Ch.1 Transmit Enable Bit in the Serial I/F Ch.1 Control Register (D7/0x300B13)
note: Do not set TXEN1 (D7/0x300B13) to 0 during a transmit operation.
(3) transmit procedure
The serial interface contains a transmit shift register and a transmit data register, which are provided indepen-
dently of those used for a receive operation.
Transmit data is written to TXD1[7:0] (D[7:0]/0x300B10).
tXD1[7:0]: Serial I/F Ch.1 Transmit Data Bits in the Serial I/F Ch.1 Transmit Data Register (D[7:0]/0x300B10)
The data written to TXD1[7:0] (D[7:0]/0x300B10) enters the transmit data buffer and waits for transmission.
The transmit data buffer is a 2-byte FIFO and up to two data can be written to it successively if empty. Older
data will be transmitted first and cleared after transmission. The next transmit data can be written to the trans-
mit data register, even during data transmission. The transmit data buffer status flag TDBE1 (D1/0x300B12) is
provided to check whether this buffer is full or not. This flag is set to 1 when the transmit data buffer has a free
space for transmit data to be written and reset to 0 when the transmit data buffer becomes full by writing trans-
mit data.
tDBe1: Serial I/F Ch.1 Transmit Data Buffer Empty Flag in the Serial I/F Ch.1 Status Register (D1/0x300B12)